The present invention relates to a liquid crystal display and a projector using the same. Particularly, this invention relates to improvement in liquid crystal display for restricting generation of interference fringes due to reflection of light caused at the interface between a transparent layer and a liquid crystal layer of the liquid crystal display.
Liquid crystal projectors have recently been used, for example, for presentation of new products using images created by computer-graphics and projected onto a screen and in home theater in which moving pictures are projected onto a large screen.
Moreover, reflective liquid crystal displays used for such projectors have been the focus of much attention for high intensity and resolution because they have a large aperture even at high pixel density.
Problems on conventional reflective liquid crystal displays are discussed with reference to FIG. 1.
A reflective liquid crystal display shown in FIG. 1 is provided with a liquid crystal layer 4 sandwiched by a transparent electrode 2 and a substrate 3 of integrated circuitry (called an IC-substrate hereinafter).
The transparent electrode 2 consists of a transparent glass substrate 5 and also a transparent electrode layer 6 and a first orientation film 7 stacked under the substrate 5.
The IC-substrate 3 consists of a silicon substrate 8 and also an active-matrix driver 9, pixel electrodes 10 and a second orientation film 11 stacked on the silicon substrate 8.
The transparent electrode 2 and the IC-substrate 3 are bonded with each other so that the first and the second orientation films 7 and 11 face each other.
In operation, a linearly-polarized reading light beam is incident from the transparent electrode 2 side to reach the pixel electrodes 10 of the IC-substrate 3 through the liquid crystal layer 4.
A light beam reflected at the pixel electrodes 10 passes through the liquid crystal layer 4 in the direction reversal of incidence and is emitted from the transparent electrode 2. The emitted light beam is projected onto a screen via a projection lens (both not shown) to display an image thereon which has been optically modulated in accordance with a video signal in the liquid crystal layer 4.
The transparent electrode layer 6 is made of a transparent conductive film, such as, ITO (Indium Tin Oxide) of high reflectivity. Thus, there is a big difference in reflectivity at the interface between the transparent electrode layer 6 and the liquid crystal layer 4.
This causes reflection, at the interface, of some beam components of the light beam which has been reflected at the pixel electrode layer 10. The beam components reflected at the interface and the input reading light beam could generate interference fringes, thus lowering quality of images projected onto the screen when the thickness of the liquid crystal layer 4 is not constant (variation in cell gap).
Liquid crystal projectors using this conventional reflective liquid crystal display is provided with a light source, such as, a metal halide lamp or a ultra-high pressure mercury lamp of high emission efficiency containing mercury as an emission triggering gas. These lamps generate strong emission lines of 440, 540 and 580 nm in an emission spectrum in visible radiation range.
Restriction of interference fringes caused by specific emission lines of light source requires control of variation in cell gap in accuracy of xcex/4 (xcex: wavelength of emission lines of light source that causes interference fringes) or lower for high consistency.
Control of variation in cell gap in such accuracy is possible in principle but not practical for mass-production.
U.S. Pat. No. 5,570,213 discloses a multi-layer anti-reflection film having a transparent electrode layer for restricting reflection at the interface, thus controlling generation of interference fringes.
The multi-layer anti-reflection film, however, requires thickness of reflectivity at 0.1% or lower, thus causing increase in production cost.
Moreover, the multi-layer anti-reflection film is made of a multi-layer non-conductive optical thin film. Coating the transparent electrode with the optical thin film causes charge storage on the film when applied electric field carries a d. c. current, which could cause image sticking on the liquid crystal layer.
Japanese Un-examined Patent Publication No. 11-337935 discloses scattered reflection-type electrode having irregularity on pixel electrodes for controlling generation of interference fringes.
Scattered radiation is, however, generated due to reflection on the pixel electrodes, which lowers contrast and intensity, thus causing degradation of displayed images.
A purpose of the present invention is to provide a liquid crystal display of high image quality and suitable to mass-production with restricted interference fringes even employing a light source of high emission efficiency to generate strong emission lines, and also a projector equipped with the liquid crystal display.
The present invention provides a liquid crystal display including: a liquid crystal layer; a first electrode substrate; and a second electrode substrate, provided as facing the first substrate so that the liquid crystal layer is sandwiched by the first and the second substrates, at least either the first or the second substrate being a transparent substrate, at least either the first or the second substrate being provided with first electrode sections each having a first height and a plurality of second electrode sections each having a second height, the first height being higher than the second height by a predetermined height, areas of the first electrode sections in total and areas of the second electrode sections in total being equal to each other on at least either the first or the second substrate.
Moreover, the present invention provides a projector including: a light source to emit a reading light beam; a filter to allow a specific light beam component only of the reading light beam to pass therethrough; a polarization beam splitter to split the light beam component in polarization; a liquid crystal display to optically modulate the light beam component, thus emitting a reflected light beam; and a projection lens to project the reflected light beam onto a screen via the polarization beam splitter, wherein the liquid crystal display has a liquid crystal layer, a first electrode substrate and a second electrode substrate provided as facing the first substrate so that the liquid crystal layer is sandwiched by the first and the second substrates, at least either the first or the second substrate being a transparent substrate, at least either the first or the second substrate being provided with first electrode sections each having a first height and a plurality of second electrode sections each having a second height, the first height being higher than the second height by a predetermined height, areas of the first electrode sections in total and areas of the second electrode sections in total being equal to each other on at least either the first or the second substrate.